Known head mounted or head-up display systems are typically used for military applications. For example, a head-up display may be mounted on a helmet worn by a pilot in order to project an image in the pilot's direct line of sight and at infinity to aid the pilot in carrying out a military operation. Such systems typically include a cathode ray tube, CRT, that is mounted on the pilot's helmet where the CRT receives video information via heavy cables that are coupled to video display generating equipment that is fixedly mounted on the aircraft. Because these systems are cumbersome, bulky and heavy, they are not suitable for consumer type applications. Further, known head mounted display systems typically utilize components such as a display and a number of optical elements that are mounted in a fixed relation to one another. Such systems typically can only accommodate a small range of head sizes. Manufacturing head mounted display systems with various fixed configurations so as to accommodate different head sizes is extremely expensive; however, if the system cannot accommodate a wide range of head sizes, the system is not suitable for consumer use since the head size among consumers varies greatly. Further, the large number of optical elements utilized in these systems adds to the cost of any one fixed configuration.
One known display system as shown in U.S. Pat. No. 5,162,828 has an optical system that includes only a single mirror. The mirror receives information directly from the display wherein the mirror is shaped to have a toroidal, parabolic or zernike polynomial reflecting surface so as to project an enlarged image at an apparent distance from the user that is greater than the actual optical path between the display, mirror and user's eye. This optical system is low cost because it utilizes a single optical element, the mirror. Further, the mirror provides a good quality virtual image for many applications. However, because the mirror includes only a single optical surface, it is difficult to shape that surface so as to minimize distortion and astigmatism.